When replace a new iPhone 6 plus screen, those problems occurred frequently:
1. No touch function during the process of LCD testing or finished installing.
2. The screen flickers by slightly touching, then without touch function.
3. In a few days, the new replaced screen can not work any more.
Usually we regard them as the matter of LCD screen, and replace a new lcd to solve those problems, but bad touch happens again. Through uninterruptedly attempting, we find it is the problem of touch IC. Replace a new lcd screen can not solve the problem fundamentally.
Why it is the problem of touch IC? Let’s see how it works firstly.
Touch screen is a kind of induction type LCD Display device which can receive contact etc input signal, When contacting a graphical on-screen buttons, haptic feedback system can drive a variety of on-screen coupling device according to a pre -programmed program which can be used to replace the mechanical button panel , and by the LCD screen to create a vivid video effect .
To put it simply, when we touch one point of the screen , touch sensor will collect the according location data and transmit it to touch ic for integration , then touch IC convert the message into display information and transmit to display IC, finally display IC turned the information into corresponding pictures for displaying or changing.
The above three phenomena occur are due to touch sensor can not transmit the received information to display IC, so we can judge it is the problem of touch IC.
Then how to work it out?
1). Find U2402 touch IC and dismantle.
2).Test the resistance of U2402, and find M1 has no resistance.
3).Fly line from M1 to one part of U2403 (Note: In practice, flying line is the essential step for screen flicker and bad touch).
4).Reinstall U2402 touch IC
5). Install and test whether it works after cooling.
In general, bad touch and screen flicker are supposed to the problem of lcd screen, then how to simple judge the problems? When we fall into the situation of bad touch, we can test several lcds with the same mainboard, or choose a good lcd for testing, then you can decide which part goes wrong.
For more details, you can click here: https://www.youtube.com/watch?v=fJ3JC1-45nY